I have a 99 F250 SD, with the Powerstroke, It just turned 220,000 miles and the speedo works fine up to 36 mph, then just stays at 36 no matter how fast the truck is moving. If I floor the truck, the speedo goes down to "0" and back to 36 when I let off? the cruise control also quit along with the speedo (im sure they are related)
I changed the sensor on the trans, but that didnt change anything. Could it be the speedo head? sounds electical?

Thanks In advance, Frank

 

Did you check the VSS sensor on top of the rear end? NAPA call this sensor the ABS sensor. Check the connection on the sensor. That is what I would check first.